Ultra-low density aerogel optical applications

1993 ◽  
Vol 8 (2) ◽  
pp. 352-355 ◽  
Author(s):  
S.P. Hotaling
Keyword(s):  
Surface Topology ◽  
Low Density ◽  
High Porosity ◽  
Fractal Surface ◽  
Surface Geometry ◽  
Surface Machining ◽  
Low Weight ◽  
Optical Applications ◽  
Materials Used ◽  
Reflective Coatings

Despite the extremely low density and the hence low weight of aerogel materials, the applicability of these materials to reflective applications has had little attention due to the high porosities exhibited by the materials. This high porosity yields an intrinsically rough but uniform surface topology for aerogel of density in the low hundreds of milligrams per cubic centimeter and a fractal surface geometry for lower density aerogel (densities of the order of tens of milligrams per cubic centimeter). This paper presents new results of aerogel materials used as ultra-light substrates for reflective coatings by way of surface machining, polishing, and planarization prior to metallization, and the optical characterization thereof.

Optical and Mechanical Properties of Aluminum Film Deposited on Glass Substrate

2010 ◽  
Vol 297-301 ◽  
pp. 444-449 ◽  
Author(s):  
Shiuh Chuan Her ◽  
Yi Hsia Wang
Keyword(s):  
Wavelength Region ◽  
Aluminum Film ◽  
Surface Topology ◽  
Aluminum Films ◽  
Glass Substrates ◽  
Atomic Force ◽  
Environmental Test ◽  
Optical Applications ◽  
Optical And Mechanical Properties ◽  
Al Thin Film

The aluminum film with high reflectivity and low absorption in the visible wavelength region has been widely used in optical applications. In this investigation, aluminum films were prepared on glass substrates by electron-beam vapor deposition. The reflectivity of the Al thin film was measured by a Perkin-Elmer Lambda spectrophotometer in the wavelength region of 450-680 nm. The experimental measurements of reflectivity were validated with the numerical results using the Essential Macleod software. The surface topology and microstructure of the film were examined by means of atomic force microscope (AFM). The effects of the temperature and humidity on the reflectivity of the Al film were examined by the environmental test. Nanoindentation tests were employed to determine the hardness and Young’s modulus of the film. The measured hardness of the Al thin films were found to depend on the penetration depth.

Distributed-Parameter Modeling for Geometry Control of Manufacturing Processes With Material Deposition

1998 ◽  
Vol 122 (1) ◽  
pp. 71-77 ◽  
Author(s):  
Charalabos Doumanidis ◽  
Eleni Skordeli
Keyword(s):  
Solid Freeform Fabrication ◽  
Surface Topology ◽  
Distributed Parameter ◽  
Surface Geometry ◽  
Mass Source ◽  
Freeform Fabrication ◽  
Geometry Model ◽  
Material Deposition ◽  
Solid Objects ◽  
3D Solid

Recent solid freeform fabrication methods generate 3D solid objects by material deposition in successive layers made of adjacent beads. Besides numerical simulation, this article introduces an analytical model of such material addition, using superposition of unit deposition distributions, composed of elementary spherical primitives consistent with the mass transfer physics. This real-time surface geometry model, with its parameters identified by in-process profile measurements, is used for Smith-prediction of the material shape in the unobservable deposition region. The model offers the basis for a distributed-parameter geometry control scheme to obtain a desired surface topology, by modulating the feed and motion of a moving mass source. The model was experimentally tested on a fused wire deposition welding station, using optical sensing by a scanning laser stripe. Its applications to other rapid prototyping methods are discussed. [S0022-0434(00)02301-7]

Aerogels as promising materials for antibacterial applications: a mini-review

2021 ◽  
Author(s):  
Gulcihan Guzel Kaya ◽  
Elena Aznar ◽  
Huseyin Deveci ◽  
Ramón Martínez-Máñez
Keyword(s):  
Antibacterial Activity ◽  
Low Density ◽  
High Porosity

Aerogels with ultra-low density, high porosity, tunable sizes, and biocompatibility have been regarded as promising carriers for antibacterial applications. Different approaches can be followed to obtain such beneficial antibacterial activity.

scholarly journals Continuous, Strong, Porous Silk Firoin-Based Aerogel Fibers toward Textile Thermal Insulation

Polymers ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 1899 ◽  
Author(s):  
Haiwei Yang ◽  
Zongqian Wang ◽  
Zhi Liu ◽  
Huan Cheng ◽  
Changlong Li
Keyword(s):  
Heat Transfer ◽  
Thermal Insulation ◽  
Hollow Fiber ◽  
High Performance ◽  
Large Scale ◽  
Low Density ◽  
Potential Candidate ◽  
Scale Production ◽  
Insulation Material ◽  
High Porosity

Aerogel fiber, with the characteristics of ultra-low density, ultra-high porosity, and high specific surface area, is the most potential candidate for manufacturing wearable thermal insulation material. However, aerogel fibers generally show weak mechanical properties and complex preparation processes. Herein, through firstly preparing a cellulose acetate/polyacrylic acid (CA/PAA) hollow fiber using coaxial wet-spinning followed by injecting the silk fibroin (SF) solution into the hollow fiber, the CA/PAA-wrapped SF aerogel fibers toward textile thermal insulation were successfully constructed after freeze-drying. The sheath (CA/PAA hollow fiber) possesses a multiscale porous structure, including micropores (11.37 ± 4.01 μm), sub-micron pores (217.47 ± 46.16 nm), as well as nanopores on the inner (44.00 ± 21.65 nm) and outer (36.43 ± 17.55 nm) surfaces, which is crucial to the formation of a SF aerogel core. Furthermore, the porous CA/PAA-wrapped SF aerogel fibers have many advantages, such as low density (0.21 g/cm3), high porosity (86%), high strength at break (2.6 ± 0.4 MPa), as well as potential continuous and large-scale production. The delicate structure of multiscale porous sheath and ultra-low-density SF aerogel core synergistically inhibit air circulation and limit convective heat transfer. Meanwhile, the high porosity of aerogel fibers weakens heat transfer and the SF aerogel cellular walls prevent infrared radiation. The results show that the mat composed of these aerogel fibers exhibits excellent thermal insulating properties with a wide working temperature from −20 to 100 °C. Therefore, this SF-based aerogel fiber can be considered as a practical option for high performance thermal insulation.

scholarly journals In-Depth Study into Polymeric Materials in Low-Density Gastroretentive Formulations

Pharmaceutics ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 636
Author(s):  
Nieves Iglesias ◽  
Elsa Galbis ◽  
Lucía Romero-Azogil ◽  
Elena Benito ◽  
Ricardo Lucas ◽  
...  
Keyword(s):  
Polymeric Materials ◽  
Dosage Forms ◽  
Oral Dosage ◽  
Low Density ◽  
Rapid Transit ◽  
Pharmacokinetic Properties ◽  
Depth Study ◽  
Resident Time ◽  
Materials Used ◽  
Oral Dosage Forms

The extensive use of oral dosage forms for the treatment of diseases may be linked to deficient pharmacokinetic properties. In some cases the drug is barely soluble; in others, the rapid transit of the formulation through the gastrointestinal tract (GIT) makes it difficult to achieve therapeutic levels in the organism; moreover, some drugs must act locally due to a gastric pathology, but the time they remain in the stomach is short. The use of formulations capable of improving all these parameters, as well as increasing the resident time in the stomach, has been the target of numerous research works, with low-density systems being the most promising and widely explored, however, there is further scope to improve these systems. There are a vast variety of polymeric materials used in low-density gastroretentive systems and a number of methods to improve the bioavailability of the drugs. This works aims to expedite the development of breakthrough approaches by providing an in-depth understanding of the polymeric materials currently used, both natural and synthetic, their properties, advantages, and drawbacks.

scholarly journals Robust polyimide nano/microfibre aerogels welded by solvent-vapour for environmental applications

2019 ◽  
Vol 6 (8) ◽  
pp. 190596 ◽  
Author(s):  
Ying Shen ◽  
Dawei Li ◽  
Bingyao Deng ◽  
Qingsheng Liu ◽  
Huizhong Liu ◽  
...  
Keyword(s):  
Compressive Strain ◽  
Building Blocks ◽  
Uniform Structure ◽  
Low Density ◽  
High Porosity ◽  
Air Filtration ◽  
Solvent Vapour ◽  
Fibrous Network ◽  
Aerosol Filtration ◽  
New Perspective

Due to the high porosity, resilience and ultra-low density, polymer nanofibre-derived aerogels (NFAs) have been widely investigated in recent years. However, welding of the fibrous networks of NFAs, which has been proved extremely essential to their structural performance, still remains a major challenge. Herein, electrospun polyimide (PI) nano/microfibres were used as building blocks to construct hierarchically porous aerogels through a solid-templating technique. By further welding the adjacent nano/microfibres at their cross-points in a controllable fashion by solvent-vapour, super elasticity was achieved for the aerogels, with a recoverable ultimate strain of 80%. It is noteworthy that this process is free from cross-linking, heating and significant structure changing (i.e. chemical structure, crystallinity and fibrous network). Additionally, the porous structure of PI nano/microfibre aerogels (PI-N/MFAs) could be tuned by adjusting the organization of microfibres from a disordered/ordered cellular to a uniform structure. The as-obtained aerogels showed ultra-low density (4.81 mg cm −3 ), high porosity (99.66%), and comparable or higher recoverable compressive strain and stress relative to the other nanofibre-based aerogels. Furthermore, we showed the potential of such an aerogel for particle or aerosol filtration. PI nanofibre aerogels composite filters (PI-NFACFs) manifested excellent performance in PM 2.0 filtration (99.6% filtration efficiency with 115 Pa pressure drop). Therefore, this study brought a new perspective on the simple preparation of nanofibre-based aerogels for air filtration.

scholarly journals High-Porosity Thermal Barrier Coatings from High-Power Plasma Spray Equipment—Processing, Performance and Economics

Coatings ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 957
Author(s):  
Nicholas Curry ◽  
Matthias Leitner ◽  
Karl Körner
Keyword(s):  
Thermal Barrier Coatings ◽  
High Power ◽  
Deposition Efficiency ◽  
Sintering Behavior ◽  
Thermal Barrier ◽  
Low Density ◽  
High Porosity ◽  
Plasma System ◽  
Barrier Coatings ◽  
The Impact

High-porosity thermal barrier coatings are utilized on gas turbine components where maximizing the coating thermal insulation capability is the primary design criteria. Though such coatings have been in industrial use for some time, manufacturing high-porosity coatings quickly and efficiently has proven challenging. With the industry demand to increase productivity and reduce waste generation, there is a drive to look at improved coating manufacturing methods. This article looks at high-porosity coatings manufactured using a high-power plasma system in comparison with a current industrial coating. A commercial spray powder is compared with an experimental Low-Density powder developed to maximize coating porosity without sacrificing coating deposition efficiency. The resultant coatings have been assessed for their microstructure, adhesion strength, furnace cyclic lifetime, thermal conductivity and sintering behavior. Finally, the impact of spray processing on coating economics is discussed. The use of a Low-Density powder with a high-power plasma system allows a high-porosity coating to be manufactured more efficiently and more cost effectively than with conventional powder feedstock. The improvement in thermal properties for the experimental coating demonstrates there is scope to improve industrial coatings by designing with specific thermal resistance rather than thickness and porosity as coating requirements.

Rigid Polyurethane Foam: A Versatile Energy Efficient Material

2016 ◽  
Vol 678 ◽  
pp. 88-98 ◽  
Author(s):  
Harpal Singh
Keyword(s):  
Thermal Conductivity ◽  
Polyurethane Foam ◽  
Weight Ratio ◽  
Building Envelope ◽  
Polymerization Reaction ◽  
Low Density ◽  
High Porosity ◽  
Rigid Polyurethane Foam ◽  
Low Thermal Conductivity ◽  
Moisture Permeability

Rigid polyurethane foam (RPUF) is typically prepared by the reaction of an isocyanate, such as methyl diphenyl diisocyanate (MDI) with a polyol blend. During the polymerization reaction, a blowing agent expands the reacting mixture. The finished product is a solid, cellular polymer with a high thermal resistance. RPUF is an outstanding material for different applications. It has many desirable properties such as low thermal conductivity, low density, low water absorption, low moisture permeability, excellent dimensional stability, high strength to weight ratio. So, it is the best insulating material for industrial buildings, cold storages, telecom and defense shelters due to low thermal conductivity, low density, low moisture permeability and high porosity. It works to reduce heating and cooling loss, improving the efficiency of the building envelope. Thus, RPUF insulation in building envelopes brings additional benefits in energy savings, resulting in lower energy bills and protecting the environment by cutting CO2 emissions.

Specific Heat Measurements of Ti6Al4V/Nano SiCp Composite

2017 ◽  
Vol 14 (1) ◽  
pp. 742-746
Author(s):  
S Krishnamohan ◽  
S Ramanathan ◽  
V Ramakrishnan
Keyword(s):  
Heat Capacity ◽  
Weight Ratio ◽  
Thermal Control ◽  
Ti6al4v Alloy ◽  
Thermal Design ◽  
Thermal Method ◽  
Scanning Calorimetry ◽  
Low Weight ◽  
Wide Range ◽  
Materials Used

The elevated strength, low weight ratio and excellent corrosion resistance intrinsic to titanium and its alloys has led to a wide range of successful applications which ensures high levels of unswerving performance in aerospace. The performance of the Thermal Control System extremely depends on the thermal behavior of the materials used in its elements. The measurements of the thermal properties of materials are necessary for better understanding of the thermal design. Differential scanning calorimetry (DSC) is the most extensively used thermal method for finding wealth of information about a material. The heat capacity (Cp) of a material was established quantitatively using DSC. The measurement was made by heating a very small quantity of the Ti6Al4V alloy and Ti6Al4V/Nano SiCp composites. Mechanical alloying (MA) and Powder metallurgy (P/M) techniques were used to fabricate the Ti6Al4V alloy and Ti6Al4V/ nano SiCp composites. The heat flow reaction was recorded as a function of definite sample temperature range from −100 °C to 375 °C. The measurements of the heat capacity of each sample in three runs were recorded by DSC. The heat capacity (Cp) of specimens is reported in this study.

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